Severe trauma and disease can lead to significant amounts of bone loss. In some instances, it is necessary to excise intercalary bone from a long bone, that is, part of the diaphysis or bone shaft between the ends of the long bone, but it is not necessary to excise the ends of the long bone. Thus, for example, a portion of the shaft of the humerus may need to be excised to remove a malignancy, while the ends of the humerus defining parts of the shoulder and elbow joint may be healthy. Similarly, it may be necessary to excise part of the shaft of the tibia or femur while the ends of these bones are healthy. Rather than remove the healthy ends of the bone, it may be desirable to leave the healthy portions of the bone in place and remove the damaged or diseased bone. In these circumstances, the empty span between the ends of the bone must be replaced with some type of mid-shaft prosthesis that spans the distance between the native bone ends. The mid-shaft prosthesis can include stems that fit into the intramedullary canals of the native bone ends and a body that extends between these stems. However, it may be difficult to implant such a mid-shaft prosthesis. Implantation can require that the native bone ends be distracted proximally and distally in order to fit the mid-shaft prosthesis into position. Since the native bone ends are surrounded by and connected to soft tissue, distraction of the native bone ends can damage the soft tissue and the connections between the soft tissue and the native bone ends.
Moreover, different bones undergo different types of stress in use. For example, the femur and tibia will tend to be subjected to compressive forces, while the humerus, radius and ulna will tend to be subjected to tension.